1. Field of the Invention
The present invention generally relates to wall bracing systems. More particularly, this invention relates to a method and apparatus for bracing a wall that has begun to buckle inward as a result of hydrostatic pressure and/or other external forces as may occur with the foundation or basement walls of a building.
2. Description of the Prior Art
Various wall bracing systems are known, as evidenced by U.S. Pat. Nos. 377,940, 4,189,891, 4,353,194 and 5,845,450. The latter patent, U.S. Pat. No. 5,845,450 to Larsen, employs a rigid I-beam that is placed flush against a masonry basement wall and secured at its upper end with threaded rods welded to a bracket fastened to a single floor joist. If the joist runs perpendicular to the wall, the rods are cantilevered from the joist by the bracket. With the rods, a force is applied by the I-beam to the wall. Larsen""s bracing system relies on the inherent rigidity of the I-beam to provide a sufficiently straight (flat) support to prevent buckling of an existing straight (unbuckled) basement wall. However, the force that can be applied by the cantilevered rod and bracket assembly through the I-beam to the wall is significantly limited. Notably, Larsen teaches that the bracing system can also be used to straighten a wall that has already buckled, i.e., further movement of the wall into contact with the I-beam will result in the wall becoming straight again, though inherently inclined. Accordingly, it would be contrary to the teachings of Larsen that his I-beam would be intended or allowed to bend to any significant degree when used to brace a basement wall.
In view of the above, a disadvantage of using an I-beam to brace a masonry wall that has already begun to buckle is that the beam only makes contact with the wall at a single point, corresponding to a tangent of the curvature of the buckled wall. Any further support offered by the beam occurs only after the wall has buckled further, i.e., individual blocks of the wall have moved into contact with portions of the beam not originally contacting the wall. Consequently, the use of an I-beam to brace a buckled masonry wall does not initially stabilize the wall, which can allow significant damage to occur to the wall and the structure supported by the wall. Furthermore, because of the rigidity of an I-beam, over the course of a year gaps can appear where contact between the beam and wall originally existed due to seasonal freezing and thawing. Consequently, to stabilize the wall throughout the year, shims must be installed between the beam and wall to reestablish positive contact therebetween.
In view of the above, what is needed is an improved method of bracing a wall that has already begun to buckle.
The present invention provides a wall bracing system that uses a beam capable of bending to conform to a masonry wall that has partially buckled inward from external forces, such as hydrostatic pressures to which basement walls are typically exposed. The bracing system of this invention applies a relatively uniform pressure against the wall to prevent further inward movement.
The bracing beam employed by this invention is required to be sufficiently flexible to conform to a partially buckled wall. A preferred beam is an American Standard steel channel having any standard flange width, such that the beam is more readily elastically deformable in a direction perpendicular to its web and opposite the flanges. One end of the beam is secured to the basement floor adjacent the foundation wall, preferably immediately adjacent the wall. The upper end of the beam is held in place with a bracket system bolted to overhead floor joists. The bracket system applies a force against the upper end of the beam toward the wall. Sufficient pressure is applied by the bracket system so that at least that portion of the beam above the point of maximum horizontal wall displacement (e.g., the primary fracture point of the wall), more preferably the entire length of the beam, contacts and conforms to the buckled portion of the wall. As a result, the beam is prestressed when installed, making positive contact with the wall that is not interrupted by any inward or outward movement of the wall. As a result, once installed, the bracing system does not require adjustments or close monitoring. Instead, the prestressed beam moves with the seasonal movement of the walls as temperature and moisture changes occur, while preventing further buckling of the wall.
Other objects and advantages of this invention will be better appreciated from the following detailed description.